This application addresses the need at Johns Hopkins University for increased capacity to perform high speed cell sorting of specimens infected with human immunodeficiency virus (HIV) type 1 and related retroviruses. It specifically requests support for the purchase of a Cytomation MoFlo cell sorter, to be house in a biosafety level 3 laboratory in the Johns Hopkins School of Hygiene and Public Health. The request is necessary for research programs at Johns Hopkins to take advantage of recent exciting findings and methodological advances that promise important progress in understanding disease mechanisms in AIDS. The cell sorting core facility to be modernized with this purchase was begun in 1989 with construction of new laboratory space designed specifically for HIV research, and acquisition of a cell sorter (Coulter ELITE) that was close to state-of-the-art t the time. Both of these enterprises were supported by grants obtained for the specific purpose of establishing a cell sorting core facility for biohazardous specimens. The facility has been successful in that it has been increasingly well used for AIDS research. However, we have reached the point where the sorting capacity of the ELITE (2500-3500 cells/second for most applications is severely limiting research that could otherwise be done. The Cytomation MoFlo, based on data from several laboratories, could increase sorting speed and throughput by at least 5-fold and represents the most cost-effective method for alleviating the current bottleneck. Particularly benefitted by the improved sorting capacity requested would be research in 3 areas: host defense against HIV, the establishment of viral reservoirs that cna persist despite potent new anti-retroviral therapies,a nd the effect of HIV infection on turnover and renewal of human immune cells. Specific research projects of 7 investigators that would so benefit are described. Procedures and plans for the cell sorting facility are described for continuing it service and productivity in the future. The instrumentation requested will be well utilized by the facility, overseen by a full time cytometer operator, a facility director, and an internal advisory committee. This instrumentation will also allow the Johns Hopkins AIDS research community to meet its research agenda for the next several years as we struggle for treatments and vaccines against this scourge.